Screw cap



FIG. 1 is a perspective view of a screw cap, the two sides not shown being identical to those shown;

FIG. 2 is a top view of the screw cap of FIG. 1;

FIG. 3 is a perspective view of a second embodiment of a screw cap similar to that of FIG. 1 but larger in size, the two sides not shown being identical to those shown; and,

FIG. 4 is a top view of the screw cap of FIG. 3. 

The ornamental design for a screw cap, as shown and described. 